In the field of work vehicles, particularly those vehicles which perform digging or loading functions such as excavators, backhoe loaders, and front shovels, the work implements are generally controlled with two or more operator controls in addition to other vehicle function controls. The manual control system often includes foot pedals as well as hand operated levers. The Case backhoe, for example, employs three levers and two pedals to control the digging implement, and the Ford backhoe has four levers to control the same. There are serious drawbacks associated with these implement control schemes. One is operator stress and fatigue resulting from having to manipulate so many levers and pedals. A vehicle operator is required to possess a relatively high degree of expertise to manipulate and coordinate the multitude of control levers and foot pedals proficiently. To become productive, an inexperienced operator also requires a long training period to be familiar with the controls and their functions.
Some manufacturers recognize the disadvantages of having too many controls, and have adopted a two-lever control scheme as the norm. Generally, the two vertically mounted two-axis levers share the task of controlling linkages (boom, stick, and bucket) of the work implement. For example, presently Caterpillar excavators employ one joystick for stick and swing control, and another joystick for boom and bucket control. Similarly, John Deere has a joystick for boom and swing control, and another for stick and bucket control. In each instance, the number of controls has decreased to two, making machine operation much more manageable. However, the two-lever control scheme presently used in the industry still has an undesirable property. As can be easily seen from the Caterpillar and Deere machines, the assignment of implement linkages to the joysticks is entirely arbitrary, and there exists little correlation between the direction of movement of the work implement linkages and those of the control levers. Thus, to cause the boom to rise, the stick to move toward the vehicle and the bucket to curl as in a typical leveling operation on a Caterpillar excavator, the operator manipulates the right-hand joystick diagonally toward the rear and left of the vehicle for bucket curl and boom raise, and the left-hand joystick toward the rear of the vehicle for stick movement. This is contrary to natural expectations and requires acute concentration of even an experienced operator, resulting in fatigue, mental stress, and diminished productivity. Furthermore, because there is no industry standard, inconsistencies abound between manufacturers and even among different excavator-type machines within a single manufacturer. Such inconsistencies compromises the ability and productivity of even the most skilled operator to adapt to different equipment and to different manufacturers.
The requirement of correlating the implement movement intuitively to the controls has only been partially satisfied in known systems.
One such system is described in U.S. Pat. No. 4,059,196 issued to Uchino et al. on Nov. 22, 1977. The control system disclosed therein includes a manual control lever in the form of a miniature work implement consisting of a miniature boom, stick and bucket. To dig, the operator in effect manipulates all three elements of the miniature control implement to go through the same motions as the digging implement. Uchino's master-slave control system addresses the problem of correlating the controls to the work implement, but the three-element control lever effectively is a three lever control system that inherently has the same aforementioned multiple control problems. Furthermore, the control system not only does not afford the operator a comfortable grip, it is also awkward to manipulate, position, and coordinate all three elements to mimic the normal course of operations of the boom, stick, and bucket. The control lever is also not of conventional design requiring special manufacture.
Another known system described in U.S. Pat. No. 4,645,030 issued to von Bernuth et al. on Feb. 24, 1987. Von Bernuth disclosed a multi-function directional control unit that contains various control levers, switches, and buttons in which each separate control element is associated with a work movement. Although the direction of the human control movements mostly agree with that of the implement movements controlled, the interface constituted by von Bernuth's control unit is not intuitive, nor does it conform to natural expectations. Furthermore, It still requires that the operator become familiar with the one to one mapping of each control element to its respective function, and the multiple control elements easily make operating the machine confusing and demanding. This system is also of special design requiring special manufacture.
The present invention is directed to overcome the problems as set forth above.